We're always experimenting and testing ways to deliver relevant and new kinds of ads, and as part of that, we recently started running a test of an ad serving technology that will help us understand online ad serving better, and allow us to experiment with some new approaches to privacy for third-party ad servers. The privacy features we'll test in these experiments follow some recently-announced policies, such as a shorter expiration date for the cookie set on your computer and anonymization of the logs data after 18 months.

In our ad-serving tests, we're introducing an opt-out mechanism so people can opt out of the test ad-serving cookie if they wish. In addition, we’re going to experiment with ways the industry could provide improved transparency for consumers and providing users with additional controls over the data gathered by ad servers. Some of the ideas we're exploring include:

using "crumbled" cookies, so that the data typically associated with one unique identifying number or "cookie ID" will be broken up among multiple different cookies and diffuse the ad history of individual users;

providing better forms of notice within ads, to help users understand who is serving the ads they see, and what data is being collected; and

giving users the ability to provide feedback to us about the ads they like and don't like.

Like all experiments, these ideas may or may not work out. And they won't be effective unless the industry adopts them -- we are not likely to implement these ideas alone. But we are excited to start innovating in this area for our advertising customers and for our users. We welcome your feedback.